Source code
Revision control
Copy as Markdown
Other Tools
/*
* jdct.h
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1994-1996, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2015, 2022, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
* This include file contains common declarations for the forward and
* inverse DCT modules. These declarations are private to the DCT managers
* (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms.
* The individual DCT algorithms are kept in separate files to ease
* machine-dependent tuning (e.g., assembly coding).
*/
#include "jsamplecomp.h"
/*
* A forward DCT routine is given a pointer to a work area of type DCTELEM[];
* the DCT is to be performed in-place in that buffer. Type DCTELEM is int
* for 8-bit samples, JLONG for 12-bit samples. (NOTE: Floating-point DCT
* implementations use an array of type FAST_FLOAT, instead.)
* The DCT inputs are expected to be signed (range +-_CENTERJSAMPLE).
* The DCT outputs are returned scaled up by a factor of 8; they therefore
* have a range of +-8K for 8-bit data, +-128K for 12-bit data. This
* convention improves accuracy in integer implementations and saves some
* work in floating-point ones.
* Quantization of the output coefficients is done by jcdctmgr.c. This
* step requires an unsigned type and also one with twice the bits.
*/
#if BITS_IN_JSAMPLE == 8
#ifndef WITH_SIMD
typedef int DCTELEM; /* 16 or 32 bits is fine */
typedef unsigned int UDCTELEM;
typedef unsigned long long UDCTELEM2;
#else
typedef short DCTELEM; /* prefer 16 bit with SIMD for parellelism */
typedef unsigned short UDCTELEM;
typedef unsigned int UDCTELEM2;
#endif
#else
typedef JLONG DCTELEM; /* must have 32 bits */
typedef unsigned long long UDCTELEM2;
#endif
/*
* An inverse DCT routine is given a pointer to the input JBLOCK and a pointer
* to an output sample array. The routine must dequantize the input data as
* well as perform the IDCT; for dequantization, it uses the multiplier table
* pointed to by compptr->dct_table. The output data is to be placed into the
* sample array starting at a specified column. (Any row offset needed will
* be applied to the array pointer before it is passed to the IDCT code.)
* Note that the number of samples emitted by the IDCT routine is
* DCT_scaled_size * DCT_scaled_size.
*/
/* typedef inverse_DCT_method_ptr is declared in jpegint.h */
/*
* Each IDCT routine has its own ideas about the best dct_table element type.
*/
typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */
#if BITS_IN_JSAMPLE == 8
typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */
#define IFAST_SCALE_BITS 2 /* fractional bits in scale factors */
#else
typedef JLONG IFAST_MULT_TYPE; /* need 32 bits for scaled quantizers */
#define IFAST_SCALE_BITS 13 /* fractional bits in scale factors */
#endif
typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */
/*
* Each IDCT routine is responsible for range-limiting its results and
* converting them to unsigned form (0.._MAXJSAMPLE). The raw outputs could
* be quite far out of range if the input data is corrupt, so a bulletproof
* range-limiting step is required. We use a mask-and-table-lookup method
* to do the combined operations quickly. See the comments with
* prepare_range_limit_table (in jdmaster.c) for more info.
*/
#define IDCT_range_limit(cinfo) \
((_JSAMPLE *)((cinfo)->sample_range_limit) + _CENTERJSAMPLE)
#define RANGE_MASK (_MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */
/* Extern declarations for the forward and inverse DCT routines. */
EXTERN(void) _jpeg_fdct_islow(DCTELEM *data);
EXTERN(void) _jpeg_fdct_ifast(DCTELEM *data);
EXTERN(void) jpeg_fdct_float(FAST_FLOAT *data);
EXTERN(void) _jpeg_idct_islow(j_decompress_ptr cinfo,
jpeg_component_info *compptr,
JCOEFPTR coef_block, _JSAMPARRAY output_buf,
JDIMENSION output_col);
EXTERN(void) _jpeg_idct_ifast(j_decompress_ptr cinfo,
jpeg_component_info *compptr,
JCOEFPTR coef_block, _JSAMPARRAY output_buf,
JDIMENSION output_col);
EXTERN(void) _jpeg_idct_float(j_decompress_ptr cinfo,
jpeg_component_info *compptr,
JCOEFPTR coef_block, _JSAMPARRAY output_buf,
JDIMENSION output_col);
EXTERN(void) _jpeg_idct_7x7(j_decompress_ptr cinfo,
jpeg_component_info *compptr, JCOEFPTR coef_block,
_JSAMPARRAY output_buf, JDIMENSION output_col);
EXTERN(void) _jpeg_idct_6x6(j_decompress_ptr cinfo,
jpeg_component_info *compptr, JCOEFPTR coef_block,
_JSAMPARRAY output_buf, JDIMENSION output_col);
EXTERN(void) _jpeg_idct_5x5(j_decompress_ptr cinfo,
jpeg_component_info *compptr, JCOEFPTR coef_block,
_JSAMPARRAY output_buf, JDIMENSION output_col);
EXTERN(void) _jpeg_idct_4x4(j_decompress_ptr cinfo,
jpeg_component_info *compptr, JCOEFPTR coef_block,
_JSAMPARRAY output_buf, JDIMENSION output_col);
EXTERN(void) _jpeg_idct_3x3(j_decompress_ptr cinfo,
jpeg_component_info *compptr, JCOEFPTR coef_block,
_JSAMPARRAY output_buf, JDIMENSION output_col);
EXTERN(void) _jpeg_idct_2x2(j_decompress_ptr cinfo,
jpeg_component_info *compptr, JCOEFPTR coef_block,
_JSAMPARRAY output_buf, JDIMENSION output_col);
EXTERN(void) _jpeg_idct_1x1(j_decompress_ptr cinfo,
jpeg_component_info *compptr, JCOEFPTR coef_block,
_JSAMPARRAY output_buf, JDIMENSION output_col);
EXTERN(void) _jpeg_idct_9x9(j_decompress_ptr cinfo,
jpeg_component_info *compptr, JCOEFPTR coef_block,
_JSAMPARRAY output_buf, JDIMENSION output_col);
EXTERN(void) _jpeg_idct_10x10(j_decompress_ptr cinfo,
jpeg_component_info *compptr,
JCOEFPTR coef_block, _JSAMPARRAY output_buf,
JDIMENSION output_col);
EXTERN(void) _jpeg_idct_11x11(j_decompress_ptr cinfo,
jpeg_component_info *compptr,
JCOEFPTR coef_block, _JSAMPARRAY output_buf,
JDIMENSION output_col);
EXTERN(void) _jpeg_idct_12x12(j_decompress_ptr cinfo,
jpeg_component_info *compptr,
JCOEFPTR coef_block, _JSAMPARRAY output_buf,
JDIMENSION output_col);
EXTERN(void) _jpeg_idct_13x13(j_decompress_ptr cinfo,
jpeg_component_info *compptr,
JCOEFPTR coef_block, _JSAMPARRAY output_buf,
JDIMENSION output_col);
EXTERN(void) _jpeg_idct_14x14(j_decompress_ptr cinfo,
jpeg_component_info *compptr,
JCOEFPTR coef_block, _JSAMPARRAY output_buf,
JDIMENSION output_col);
EXTERN(void) _jpeg_idct_15x15(j_decompress_ptr cinfo,
jpeg_component_info *compptr,
JCOEFPTR coef_block, _JSAMPARRAY output_buf,
JDIMENSION output_col);
EXTERN(void) _jpeg_idct_16x16(j_decompress_ptr cinfo,
jpeg_component_info *compptr,
JCOEFPTR coef_block, _JSAMPARRAY output_buf,
JDIMENSION output_col);
/*
* Macros for handling fixed-point arithmetic; these are used by many
* but not all of the DCT/IDCT modules.
*
* All values are expected to be of type JLONG.
* Fractional constants are scaled left by CONST_BITS bits.
* CONST_BITS is defined within each module using these macros,
* and may differ from one module to the next.
*/
#define ONE ((JLONG)1)
#define CONST_SCALE (ONE << CONST_BITS)
/* Convert a positive real constant to an integer scaled by CONST_SCALE.
* Caution: some C compilers fail to reduce "FIX(constant)" at compile time,
* thus causing a lot of useless floating-point operations at run time.
*/
#define FIX(x) ((JLONG)((x) * CONST_SCALE + 0.5))
/* Descale and correctly round a JLONG value that's scaled by N bits.
* We assume RIGHT_SHIFT rounds towards minus infinity, so adding
* the fudge factor is correct for either sign of X.
*/
#define DESCALE(x, n) RIGHT_SHIFT((x) + (ONE << ((n) - 1)), n)
/* Multiply a JLONG variable by a JLONG constant to yield a JLONG result.
* This macro is used only when the two inputs will actually be no more than
* 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a
* full 32x32 multiply. This provides a useful speedup on many machines.
* Unfortunately there is no way to specify a 16x16->32 multiply portably
* in C, but some C compilers will do the right thing if you provide the
* correct combination of casts.
*/
#ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */
#define MULTIPLY16C16(var, const) (((INT16)(var)) * ((INT16)(const)))
#endif
#ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */
#define MULTIPLY16C16(var, const) (((INT16)(var)) * ((JLONG)(const)))
#endif
#ifndef MULTIPLY16C16 /* default definition */
#define MULTIPLY16C16(var, const) ((var) * (const))
#endif
/* Same except both inputs are variables. */
#ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */
#define MULTIPLY16V16(var1, var2) (((INT16)(var1)) * ((INT16)(var2)))
#endif
#ifndef MULTIPLY16V16 /* default definition */
#define MULTIPLY16V16(var1, var2) ((var1) * (var2))
#endif